1. Field of the Invention
The invention relates broadly to polymeric coating compositions suitable for providing a coating which is solderable and/or has high corrosion resistance and to substrates coated with the same. The coated substrates have improved properties, most importantly, resistance to hostile environments such as corrosive liquids and gases. Furthermore, the coated substrates the ability to be soldered without breaching the polymeric coating and/or electroplated. The invention further relates to methods for producing the polymeric coating compositions and polymer coated substrates.
2. Description of the Related Art
Several publications are referenced in this application. These references describe the state of the art to which this invention pertains, and are incorporated herein by reference.
Polymers have been grafted onto metallic substrates to form coatings that protect the substrates from a variety of environmental conditions. Typically organic coatings and paints are applied onto metallic substrates via a physical bond and act to protect the substrate from corrosive gases, solutions of high or low pH, varying relative humidity and varying temperature conditions. Such physically bonded coatings typically do not provide adequate protection against corrosion or other environmental impacts and have a tendency to become dislodged from the surface of the substrate after relatively short periods of time, particularly under stresses imposed by severe environmental conditions, e.g. the presence of acids or bases, corrosive gases such as hydrogen sulphide, sulphur dioxide and carbon dioxide.
Metal substrates have been coated with polymers by graft polymerization processes with results that are superior to those obtained where the metal substrate is coated with organic paints or coatings. Such grafted coatings are both conductive and provide a durable protective layer which is resistent to severe environmental conditions. U.S. Pat. No. 5,043,226 to Wiedeman, et al. describes methods for applying graft polymers to a variety of metal substrates such as steel, aluminum, iron and other metals.
It is important in many applications that the metal coated substrate have not only excellent corrosion and abrasion resistance as well as resistance to adverse environmental conditions, but that the coated metal also have satisfactory conductivity and solderability, so that it can be used in a variety of industrial applications. Heretofore, the art has not provided polymer coated metal substrates having both a tenaciously bound polymer layer which is corrosion resistant and the necessary properties of conductivity and solderability.